What is Mendel's law of dominance?

Mendel's law of dominance states that when an organism is heterozygous for a trait, the dominant allele will mask the effect of the recessive allele. This means that in a pair of alleles for a particular gene, if one is dominant and the other is recessive, the phenotype associated with the dominant allele will be the one that is observed in the organism. For example, if a plant has one allele for tall stems (dominant) and another for short stems (recessive), the plant will be tall because the tall allele dominates the expression of the short allele.

This principle demonstrates the way that genes interact to influence physical traits, as Mendel discovered through his experiments with pea plants. The dominant trait expresses itself regardless of whether it is paired with another dominant allele or a recessive allele. While all alleles involved in an organism's genotype hold genetic information, the law of dominance explains how certain alleles can overshadow the expression of others in determining the observable traits.